Solar and pool heating in Perth: heat pump vs solar thermal vs solar PV

If you already run solar with spare midday generation, scheduling a pool heat pump inside sunlight hours is the cheapest way to heat a Perth pool: it runs on electricity you'd otherwise export for almost nothing. Without solar, a heat pump on Synergy's Midday Saver tariff is the next best option, at roughly $284 a year for four hours of daily running. Solar thermal collectors need no power beyond the pool pump you already run, but they only heat the pool through spring, summer and autumn.

Perth's climate makes a 9-month pool season realistic. With the right system you can extend comfortable swimming from September through November and again from March through May, well past the deep-winter months. The right choice between solar thermal collectors, a heat pump, and solar PV powering a heat pump comes down to whether you already have solar, how much year-round heating matters to you, and how much you want to spend upfront.

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What are your options for heating a Perth pool?

Three approaches cover almost every Perth pool: dedicated solar thermal collectors on the roof, an electric heat pump, or an existing solar PV system timed to run a heat pump for close to nothing. Each has its own cost profile and its own heating season.

How do solar thermal roof collectors heat a pool?

Black rubber or polypropylene tubing panels sit on the roof. Pool water is pumped through the panels and heated directly by the sun, so there's no electricity cost beyond running the pool pump you already have.

Perth's high solar radiation suits this well. A properly sized system, one covering a substantial share of the pool's surface area in roof collectors, can extend the pool season noticeably and heat the water to comfortable swimming temperatures through the shoulder seasons (September–November and March–May).

A few trade-offs to weigh before you commit:

• No heating on cloudy days or through winter. There isn't enough radiation to work with.
• Heating happens only while the sun is on the collectors, not on demand.
• It won't push water to high temperatures the way an electric heat pump can.
• You need suitable north-facing roof area for the collectors.

Installation cost scales with pool size and collector material, so get a few local quotes to compare. Rubber collectors typically need replacing sooner than polypropylene ones, so ask about the warranty term before you buy.

How does a pool heat pump work?

A heat pump pulls heat from the surrounding air and moves it into the pool water, the same principle a reverse-cycle air conditioner uses to warm a room. Because it's moving heat rather than generating it from scratch, it produces more heat energy than the electricity it consumes, and that ratio improves as the outside air warms up. For more on how this technology performs in a home hot water system, see Heat pump hot water in Perth: the complete guide.

Running cost, worked example (Synergy A1, 33.26c/kWh)

A heat pump drawing 2.2kW, run for 4 hours a day across a year: 2.2kW × 4h × 365 = 3,212kWh. At the A1 rate, that's 3,212 × 33.26c, or $1,068 a year.

Shift the same 4 hours a day onto Midday Saver's super off-peak window (9am–3pm, 8.85c/kWh) and the bill drops to $284 a year, since 8.85c is roughly a quarter of the A1 rate.

Set against solar thermal, a heat pump:

• Heats to whatever target temperature you set.
• Works at night and in overcast conditions.
• Needs no roof space.

Installation cost scales with pump capacity and pool size, so again, get a few local quotes to compare.

Can solar panels power your pool heat pump for free?

If you already have solar, scheduling the pool heat pump to run during generation hours (typically 9am–3pm) means it self-consumes solar electricity instead of importing from the grid.

At the A1 rate, self-consuming solar avoids paying 33.26c/kWh for grid import. That's far better than the 2c/kWh you'd get for exporting the same electricity under the DEBS off-peak rate. Run the heat pump on surplus solar and pool heating costs close to nothing.

Setting it up:

1. Fit a timer to the pool heat pump, set to run from roughly 10am to 3pm.
2. Or install a smart pump controller that activates once solar export begins.
3. The pool holds its temperature passively between running periods, so the heat pump doesn't need to run continuously.

How much solar do you need? A 6.6kW solar system generates around 28kWh on an average full-sun day. A household drawing about 10kWh of baseline load during the day would still have roughly 18kWh of surplus available for export or self-consumption. Running a 2.2kW heat pump for 5 hours uses 11kWh, comfortably inside that surplus. If you're sizing a new system with pool heating in mind, see Perth solar panel installation: what size system do you need?.

Winter changes the maths. In June and July, Perth's solar generation drops to around 60% of its annual daily average, and cooler ambient air means the heat pump needs more energy to do the same job. Expect to top up from the grid on cloudy winter days.

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How do solar thermal, heat pump, and solar PV compare?

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Which option is right for your pool?

No solar yet? A heat pump on Midday Saver (9am–3pm, 8.85c/kWh) is the cheapest system to run, at around $284 a year for 4 hours of daily operation. Get a few quotes, since installation cost scales with pump capacity and pool size. If you're weighing up Synergy tariffs for the whole house, see Midday Saver vs A1: which Synergy tariff actually saves you money?.

Solar already on the roof, with surplus midday generation? Scheduling an existing or new heat pump to self-consume that surplus gets you close to free heating during solar hours. This is usually the strongest economic case: a near-zero marginal running cost, using solar that would otherwise export for 2c/kWh.

Want the lowest upfront spend? Solar thermal has the lowest ongoing running cost if you've got suitable north-facing roof space. Just remember it's limited to spring, summer and autumn.

Want both? Some Perth pools run solar thermal through the shoulder seasons and keep a heat pump as backup for winter or cloudy stretches. The heat pump supplements rather than carries the whole load.

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How can you cut pool pump running costs with solar?

The pool's circulation pump is a separate load from the heater. It runs for 4–12 hours a day for filtration, and wattage varies substantially by pump type and speed setting.

A variable-speed pump runs at a low wattage for routine filtration and switches to a higher wattage for backwash and other high-flow tasks. Scheduling the low-speed filtration cycle inside solar hours (9am–4pm) means the pump runs largely on solar for a household with a 6.6kW system.

A standard single-speed pump runs at a fixed, higher wattage continuously, and that adds up over a year. Replacing one with a variable-speed model can meaningfully cut that running cost, particularly once the filtration cycle is scheduled inside solar hours.

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Your pool's heating requirements depend on pool size, desired temperature, and season. Upload your Synergy bill to BillWise to see how much of your electricity cost is attributable to pool equipment and model the savings from Midday Saver timing.